I have a partitioned SP 2016 farm which I am trying to get site mailboxes working. The site is setup with HNSC and the Exchange 2016 partner application has been setup to the hnsc root site. site mailbox will provision correctly for the root site. The rest of the site collections originally had an access denied problem which I fixed with the app only permissions option. However now it seems about to complete the provisioning before presenting the following error:
Can't match SharePoint hostname to a Partner Application. ERRCODEURL02
The error is being thrown on the Exchange side.
Microsoft.Exchange.Configuration.Authorization.UrlInValidException: Can't match SharePoint hostname to a Partner Application.
The HNSC root site is a different URL to this particular site collection so the partner application settings do not match. Isn’t the specified host header supposed to address this? Thanks Ian